How does VMware ESXi Server compare to ESX Server?

Introduction

Most of you are familiar with VMware ESX Server as it has been around for so many years. ESX Server offers the "service console" built in and it is a rather large installation (in comparison to ESXi). The latest version of ESXi is "thinner" and lacks the service console. You should note that ESXi is NOT a replacement for the traditional ESX Server but, instead, an alternate version available. In my opinion, neither of these versions is "better" than another. Instead, these two versions are just "different" from one another. Let us learn how these two differ and help you determine which one is best for you.

What are the 10 major differences between VMware ESX Server and ESXi Server?

1. VMware ESXi Server has no service console

The traditional (full) ESX Server has a special built-in virtual machine called the “service console”. This service console is really a modified version of Red Hat Enterprise Linux that is installed and running in every ESX Server by default. The service console has special access to the VMware-proprietary VMFS file system. 3rd party applications can be installed in the service console and Linux-based utilities can be run in the service console. Additionally, VMware includes a number of ESX-related tools in the service console, most of which start with “esxcfg-“ and they are run by accessing the service console with SSH.

As VMware ESXi Server has no service console, there is no SSH access to the server and there are no 3rd party applications that can be installed on the server. However, there are also benefits to NOT having these features (discussed more below).

2. VMware ESXi Server uses RCLI instead of service console utilities

As ESXi doesn’t have any CLI with VMware-related or Linux utilities, VMware needed to provide a CLI interface to ESXi. What VMware came up with is the Remote Command line Interface (RCLI). This is an application that you typically install as a VM and it is used to perform scheduled or ad hock scripting on the VMware Infrastructure. The ESXi RCLI is its own command line where ESX server service console scripting would be made up of mostly Linux utilities.

Because the service console has been removed from ESXi, the footprint in memory has been reduced to just 32MB. In my opinion, it is truly amazing that you can run a hypervisor, allowing you to run virtual machines on your server, with just 32MB of RAM overhead. In comparison, the full ESX Server on disk footprint is about 2GB.

Because the hypervisor is so small, the installation happens in about 10 minutes (or so) and the server boots up in 1-2 minutes. This is quite different from the full ESX server installation and boot, both of which are longer.

4. VMware ESXi Server can be purchased as an embedded hypervisor on hardware

While ESXi is so small that it can be easily installed and can even be booted from a USB Flash disk, what is truly unique about ESXi is that it is being sold by hardware vendors as a built-in hypervisor. That means that, say, you buy a Dell server, ESXi can be built inside the server (embedded) on a flash chip, on the motherboard. There is no installation of ESXi on disk.

As there is no service console to protect with the ESX Server security profile (software firewall), the security profile configuration in ESXi is very simplistic. The ESXi security profile configuration consists of a couple of services that you can either enable or not enable with inbound access. Here is a comparison between the two:

Instead of the full ESX Server “service console” boot (which looks like a Linux server booting), ESXi has a tiny “Direct Console User Interface (DCUI)”. Unofficially, I like to call this the “yellow firmware console”. In this ESXi console, all that you can configure are some very basic ESXi server options such as the root user password, network settings, and a couple other items. In the graphic below, you can see why I call it “yellow”:

Figure 3: ESXi yellow firmware console / DCUI

Because this tiny firmware console (did I mention that it’s yellow?) has so few features, the server is virtually “stateless”. A new server can be configured in seconds because there is almost nothing to configure.

7. VMware ESXi Server has server health status built in

With ESXi some hardware monitoring features are built into the hypervisor. With ESX Server, this is not yet built in. Instead, you must install hardware monitoring software in the service console. For more information on ESXi server health status and how to install vendor-specific utilities to provide similar information on ESX Servers, please see my article: Obtaining server health status in VMware ESX and VMware ESXi.

Figure 4: ESXi Health Status

8. Some networking features are configured through the service console are not available or are experimental

As ESXi is relatively new and as ESX server has the option to install code for advanced ESX Server features, not all features available in the full ESX Server are also available in ESXi. In fact, I have had issues getting VMware High Availability (VMHA) to work in ESXi. VMHA was not officially supported on ESXi until some recent patches came out for ESXi. Still, even after the patches, I had difficulties with ESXi and VMHA.

Because the full ESX server essentially has a modified Linux system as the service console, there are many patches that have to be deployed to keep it secure. With ESXi, on the contrary, the server has very few patches that need to be applied. Because ESXi has no service console and it is considered more secure and more reliable. Security, Reliability, and Maintainability, are all major factor when considering a hypervisor.

10. You can buy VMware ESXi Server for as little as $495

With the full version of ESX Server, the least expensive purchase option is the Foundation (Starter) kit for about $1,500, while you can purchase ESXi only (with no support) for $495. On the other hand, if you do get the Foundation kit, you not only get the full ESX Server but also ESXi and a number of VMware Infrastructure Suite options. Still, obtaining ESXi for under $500 allows a server to do so much more than it ever could before.

Which version of VMware ESX Server is best for you?

I am not here to sell you on VMware, on ESX Server, or ESXi Server, what I am here to do is to inform you of the drastic differences between these two versions of “ESX Server”. In my opinion, ESX Server (full) must be used if you have 3rd party apps or if you just want to have access to the “Linux-style” service console.

On the other hand, if you are willing to give up those two benefits, with ESXi, you will get an ESXi Server that boots faster, has fewer patches to deploy, and is more reliable. ESXi is also the least expensive option.

I recommend testing both VMware ESX Server and ESXi server. Both are available for a free evaluation download from VMware Inc.

Conclusion

In this article, you learned about VMware ESX Server the differences between ESXi and ESX Server. Additionally, you learned about how to make the right choice for you. Both of these hypervisors from VMware can be evaluated at no cost.

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How does VMware ESXi Server compare to ESX Server?

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